One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,7,5)(3,4,8,6)(9,10,14,15)(11,16,18,12)(13,21,23,17)(19,20,24,22)(25,26,30,32)(27,31,34,28)(29,37,39,33)(35,36,40,38)(2,5)(3,8)(10,15)(12,16)(17,21)(20,22)(25,27,30,34)(26,31,32,28)(29,35,39,40)(33,38,37,36)(1,3)(2,6)(4,5)(7,8)(10,15)(11,18)(17,21)(19,24)(26,32)(27,34)(33,37)(35,40) involution — undirected(1,4,7,6)(2,3,5,8)(9,11,14,18)(10,16,15,12)(13,19,23,24)(17,22,21,20)(25,26)(27,31)(28,34)(29,33)(30,32)(35,38)(36,40)(37,39)(1,5,7,2)(3,4,8,6)(9,12,14,16)(10,11,15,18)(13,22,23,20)(17,24,21,19)(25,28,30,31)(26,27,32,34)(29,38,39,36)(33,40,37,35)(1,6,7,4)(2,8,5,3)(9,13,14,23)(10,17,15,21)(11,19,18,24)(12,20,16,22)(25,29)(26,33)(27,35)(28,36)(30,39)(31,38)(32,37)(34,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.